فرهنگ ریشه شناختی اخترشناسی-اخترفیزیک

M. Heydari-Malayeri - Paris Observatory

An atom made from an → antiproton and a
→ positron. In 2010 a research collaboration at CERN
combined decelerated antiprotons with positrons to produce antihydrogen atoms.
They managed 38 times to confine single antihydrogen atoms in a magnetic trap
for more than 170 milliseconds (Andersen et al. 2010, Nature, 17 Nov.).

Hydrogen, from Fr. hydrogène, from Gk. hydro-,
combining form of hydor "water" → hydro-
+ Fr. -gène "producing," → -gen;
coined in 1787 by the French chemist Guyton de Morveau (1737-1816)
because it forms water when exposed to oxygen.

hydrogen bond

بند ِ هیدروژنی

band-e hidroženi

Fr.: liaison hydrogène

The attractive force between the hydrogen attached to an electronegative
atom of one molecule and an electronegative atom of a different molecule.
Usually the electronegative atom is oxygen, nitrogen, or fluorine, which has
a partial negative charge. The hydrogen then has the partial positive charge.

The cometary cloud of hydrogen, detectable in ultraviolet light, that
is immensely bigger than even the huge visible coma it surrounds. It
is produced by the dissociation of water into hydrogen and oxygen and
by other processes set into motion by solar radiation and and the
solar wind.

A colorless or light blue liquid or gas, a triatomic cyanide,
which is extremely flammable. HCN is an important industrial chemical
and over a million tonnes are produced yearly in the world. It is produced industrially
by reacting methane and ammonia in air at high temperature.
A wide range of combustion processes produce HCN gas in the smoke or fumes.
HCN is found naturally throughout the environment at low levels as it is released
from volcanoes and certain plants and bacteria.
Hydrogen cyanide is abundant in all kinds of astronomical environments, from dark clouds to
star-forming regions and circumstellar envelopes. The first detection of
interstellar HCN (at 88.6 GHz) and H13N (at 86.3 GHz)
was reported by Buhl & Snyder (1971, ApJ 163, L47).
Also called → hydrocyanic acid and
→ prussic acid.

A phase in the life of a star that has left the
→ main sequence. When no more hydrogen is available
in the core, the core will start to contract as it is no longer releasing
the necessary energy whose pressure supports the surrounding layers.
As a result of this contraction, gravitational energy is converted into thermal energy
and the temperature will rise. Therefore a shell of unprocessed material
surrounding the original core will be heated sufficiently for hydrogen
burning to start. During the evolution of
→ asymptotic giant branch stars
hydrogen shell burning occurs alternatively with helium shell burning.
→ double shell burning.

A kind of → degenerate matter resulting from hydrogen gas
when it is sufficiently compressed to undergo a phase
change to liquid or solid state. Metallic hydrogen is thought to be present in compressed
astronomical objects, such as the interiors of the solar system planets
Jupiter and Saturn. Above the core of these planets
(at a temperature of 10,000 degrees and a pressure of 3 million bars)
the electrons are squeezed out of the hydrogen atoms and the fluid
starts to conduct like a metal.

Non-ionized → atomic hydrogen gas which constitutes an
important component of the → interstellar medium,
accounting for perhaps half its mass, even though
its density is very low. Its radio emission
→ 21-centimeter line has made it possible to map
the distribution of neutral hydrogen in the → spiral arms
of our own Galaxy and other nearby galaxies.